Psychology Chapter on Brain Functions

Central Nervous System (CNS)

• Consists of the brain and spinal cord.
• Receives sensory input.
• Directs motor neuron activity.
• Composed of gray and white matter.
  • Gray matter: neuron cell bodies and dendrites.
  • White matter: axon tracts (myelin).
• Ventricles and central canal are filled with cerebrospinal fluid (CSF).

Three Meninges

• Dura mater: tough outer membrane, closest to the skull.
• Arachnoid mater: middle membrane, below the dura mater (spider-web like).
• Pia mater: third delicate membrane adhering to the CNS surface.

Cerebral Ventricles

• Four internal fluid-filled chambers in the brain.
• Two lateral ventricles visible on scans.
• Connected by the cerebral aqueduct.

Cerebrospinal Fluid (CSF)

• Colorless fluid filling the subarachnoid space, central canal, and ventricles.
• Continuously produced by choroid plexuses (capillary networks).
• Serves to cushion and remove waste from the brain.

Cerebrum

• Largest portion of the brain (80% of mass).
• Responsible for higher mental functions.
• Corpus callosum: major axon tract connecting the right and left cerebral hemispheres.

Cerebral Lobes (continued)

• Frontal Lobe: Anterior portion, controlling voluntary muscles and containing upper motor neurons. Regions with most motor innervation have largest motor cortex areas.
• Parietal Lobe: Crucial for somatosensory perception. Body parts with higher receptor density have larger areas in the sensory cortex.
• Temporal Lobe: Contains auditory centers receiving cochlea sensory fibers. Involved in auditory and visual interpretation and association.
• Occipital Lobe: Primary area for vision and coordinating eye movements.

Cerebral Cortex

• Characterized by folds (gyri) and grooves (sulci).
• Frontal lobe's anterior portion is the site of upper motor neurons. Involvement in motor control.

Visualizing the Brain

• X-ray computed tomography (CT): Computer-processed x-ray data showing different tissue densities.
• Positron-emission tomography (PET): Injects radioisotopes to detect active brain cells based on gamma ray emission. Useful for metabolic activity maps.
• Magnetic resonance imaging (MRI): Measures proton responses to magnetic fields then radio signals enabling visualization of brain structure and function.

Electroencephalogram (EEG)

• Measures electrical activity in the brain.
• Tracks synaptic potentials at cell bodies and dendrites.
  • Used for diagnosing epilepsy and brain death.

EEG Patterns

• Alpha: Recorded in parietal and occipital areas when awake and relaxed, eyes closed.
• Beta: Strongest in frontal lobes near precentral gyrus. Indicates heightened alertness and mental activity, evoked by stimuli.
• Theta: Emitted from temporal and occipital regions. Commonly seen in newborns, severe stress in adults.
• Delta: Common during infant sleep and awareness. High amplitude and low frequency, indicates brain damage in adults.

EEG Sleep Patterns

• REM (Rapid Eye Movement): Characterized by dreams, low amplitude, high frequency oscillations (similar to waking).
• Non-REM (resting): High amplitude, low frequency waves (delta waves) with sleep spindles (waxing and waning bursts of 7-14 cycles/second) superimposed.

Cerebral Lateralization

• Cerebral dominance: Specialization of one hemisphere.
• Left hemisphere: Superior in language and analytical abilities. Damage results in severe speech problems.
• Right hemisphere: Stronger in visuospatial tasks. Damage leads to difficulties with spatial awareness and navigating.
  • Split-brain studies investigate the separate functions of left and right hemispheres when disconnected.

Language

• Broca's area: Involved in speech articulation. Damage leads to issues with speaking.
• Wernicke's area: Responsible for language comprehension. Damage leads to speech without meaning.
• Angular gyrus: Integrates auditory, visual, and somatosensory information.
• Arcuate fasciculus: Connects Wernicke's and Broca's areas to enable intelligible language. This tract delivers words to Broca's, activating speech muscles.

Emotion and Motivation

• Limbic system: network of forebrain nuclei around the brainstem mediating basic emotional drives.
• Papez circuit (closed circuit): critical for emotional regulation involving connections between the fornix, hippocampus, hypothalamus, thalamus and limbic system.
• Amygdala and hypothalamus are associated with emotional drives (like aggression or fear).
• Hypothalamus is linked with feelings, aggression, fear, feeding behavior, sexual behavior and goal-directed behaviors (using reward and punishment).

Memory

• Short-term memory: Memory of recent events.
• Medial temporal lobe: Consolidates short-term memories into long-term memories.
• Hippocampus: Crucial for acquiring new information (facts and experiences).
• Processes need both hippocampus and medial temporal lobe activity.

Long-Term Memory

• Consolidation: Converting short-term to long-term memories, involving gene activation for synaptic connections growth.
• Cerebral Cortex: Stores factual information. Visual memories are left lateralized; visuospatial on the right.
• Prefrontal lobes: Important for problem-solving, complex calculations, and planning.

Thalamus and Epithalamus

• Thalamus: Acts as a sensory relay station to the cerebrum.
• Lateral and medial geniculate nuclei: Relay visual and auditory information to cerebral cortex.
• Intralaminar nuclei: Involved in promoting alertness and arousal.
• Epithalamus: Includes choroid plexus where CSF is made and pineal gland (secretes melatonin).

Hypothalamus

• Contains centers for hunger, thirst, and body temp.
• Regulates sleep, wakefulness, emotions, feelings and behaviors, and sexual arousal.
• Stimulates hormone release from anterior pituitary.
• Produces hormones (ADH and oxytocin).
• Coordinates autonomic reflexes.

Midbrain

• Corpora quadrigemina: Superior colliculi: visual reflexes. Inferior colliculi: auditory reflexes.
• Cerebral peduncles: Fiber tract bundle, vital for ascending-descending signals.
• Substantia nigra and Red nucleus: Required for motor coordination and maintain connections between cerebrum and cerebellum.

Pons

• Connects cerebrum to cerebellum.
• Contains nuclei connected with cranial nerves V, VI, and VII
• Respiratory centers (pneumotaxic and apneustic) included within the pons.

Medulla Oblongata

• Contains ascending/descending fiber tracts reaching spinal cord.
• Includes cranial nerve nuclei (VIII–XII).
• Pyramids: Decussation of motor fibers occurs here.
• Vasomotor center controls blood vessel tone.
• Cardiac center regulates heart rate.
• Respiratory center controls, coordinated with Pons center.

Reflex Arc

• Sensory and motor response not involving conscious brain input.
• Sensory impulses are carried to spinal cord.
• Interneurons in spinal cord connect with motor neuron to transmit the impulse to effector.

Test your knowledge on various brain functions and structures with this quiz. Covering topics from EEG patterns to memory consolidation, this quiz is designed to enhance your understanding of psychology. Ideal for students studying neuroscience or psychology courses.